Running PowerShell code in powershell works, executing as .ps1 doesn't - powershell

Question

I wrote some code which tries to Get a value from one Rest API and post it to another.
I have the code saves in a .ps1 file. If I edit it and run it (or just copy and paste it into an empty PowerShell terminal) it does what I expect. However when I try to run the same .ps1 file directly I get an error on the 2nd Invoke-RestMethod.
Don't understand why I'm getting a different result and the error message not giving me many clues.
What am I doing wrong?
The code I am using is (with modified API key):
$encoded = [System.Convert]::ToBase64String([System.Text.Encoding]::UTF8.GetBytes($APIkey+":"))
$headers = #{"Content-Type" = "application/json"; "AUTHORIZATION" = "Basic $encoded"}
$APIkey = "123456789"
$metricId = "123"
$r = Invoke-RestMethod -Uri https://coinbase.com/api/v1/currencies/exchange_rates
$metric = [PSCustomObject]#{
value = [Math]::Round($r.btc_to_eur, 2)
}
$baseuri = "https://api.numerousapp.com/v1/metrics/$metricId/events"
$data = ConvertTo-Json $metric
Invoke-RestMethod -Uri $baseuri -Body $data -Headers $headers -Method Post
And the error message I get when running the .ps1 file is:
Invoke-RestMethod : :
At C:\NumerousBitcoinEur.ps1:13 char:1
+ Invoke-RestMethod -Uri $baseuri -Body $data -Headers $headers -Method Post
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException
+ FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand
I'm using PowerShell 4.0

Answer 1

$APIkey is being set after it is being used, which must be wrong. It probably works in the console because $APIkey happens to already be set.
If you like (I think it's a good idea), you can add the following to the top of your scripts to catch errors like this one.
Set-StrictMode -Version Latest